Thanks for the heads up. This did work as documented when the doc was written, but it looks like somehow the .rpo file was removed from the jail installation since then. I'll fix the doc and will create a separate ticket for the devs to fix the .rpo issue. Marking this ticket as fixed.

aria2 will resume download if the transfer is restarted.If there are any errors, then see the log file. See '-l' option in help/man page for details.Download Failed:ERROR: Failed downloading PBIbut that's not enougn, it still requires repo mirror url. And with the above repo it seems to go for the 9 version, not 9.1, and thus fails to download: